Objects and their locations in exogenous cuing.

Anatomical, physiological, and behavioral studies provide support for separate object- and location-based components of visual attention. Although studies of object-based components have usually involved voluntary attention, more recent evidence has suggested that objects may play an independent role in reflexive exogenous orienting, at least at long stimulus onset asynchronies (SOAs). In the present experiments, the role of objects in reflexive attentional orienting was investigated by developing a task in which location and object cuing could be separately examined for both short and long SOAs. Typical location cuing effects were obtained, indicating facilitation at short cue-target intervals and inhibition of return (IOR) at longer intervals. In contrast, object cuing resulted in facilitation for cued objects at long cue-target intervals and no object-based IOR. Interestingly, object cuing primarily affected targets at cued locations, and not those at uncued locations. Together, the experiments examine the interactive nature of objects and locations in exogenous orienting and seem most consistent with a location-mediated view of object-based orienting.

Auditory and visual spatial localization deficits following bilateral parietal lobe lesions in a patient with Balint's syndrome.

Lesion and electrophysiological studies indicate that the parietal lobes play a role in visual spatial attention and in computing the spatial coordinates of visual input. Fewer studies have investigated the role of the parietal lobe in auditory spatial processing, and an extensive comparison of visual and auditory spatial processing in humans with parietal lobe lesions has yet to be conducted. We have studied such localization abilities in a Balint's syndrome patient (RM) who has bilateral parietal lobe lesions. The results indicated that this patient had a significant deficit in both visual and auditory localization relative to age-matched controls. Unlike the controls, however, RM's auditory localization ability either matched or exceeded his visual localization ability depending on the task. Accordingly, RM exhibited "auditory capture," but not "visual capture" under conditions where control subjects showed the opposite pattern. These results are consistent with hypotheses that the parietal lobes are involved in creating multiple spatial representations and in shifting from one spatial reference point to another, but suggest that these parietal structures are not necessary for the integration of multiple sensory stimuli resulting in capture effects.